13.12 Histology: Liver and Pancreas

Question 1

What is the liver derived from?

Answer 1

Endoderm

Question 2

How many surfaces does a hepatocyte have and how wide is it across?

Answer 2

Polyhedral, 25um across

Question 3

How many nuclei and how many copies of DNA do hepatocytes have?

Answer 3

1-2 nuclei

tetraploid or polyploid

Question 4

What structures do hepatocytes contain (and how do these reflect their purpose)?

Answer 4

Rough ER, golgi, secretory vesicles (PRO synthesis)

Prominent smooth ER (FAT metabolism)

Many mitochondria

Question 5

What type of cells are hepatocytes?

Answer 5

Epithelial cells (replaced regularly by division of existing hepatocytes)

Question 6

Hepatocytes comprise ___% of liver weight

Answer 6

75%

Question 7

What are the blood supplies for the liver?

Answer 7

Majority, venous blood from gut (hepatic portal system)

Also arterial supply

Question 8

What surrounds the liver?

Answer 8

A thin capsule (Glisson’s capsule)

Question 9

What fibres are the hepatocytes supported by?

Answer 9

Reticular fibres (collagen type III)

Question 10

How are hepatocytes organised?

Answer 10

Into lobules (stacks of hepatocytes in plates)

Question 11

How does blood flow into the liver?

Answer 11

Into lobule, then across to central vein (outside in)

Question 12

What is the portal triad comprised of?

Answer 12

Hepatic portal vein (deoxygenated blood from gut), hepatic artery and bile duct

Question 13

Where do sinusoids converge?

Answer 13

On the central vein (carrying blood to hepatic vein and out of liver)

Question 14

What is a sinusoid?

Answer 14

A network that veins and arteries give rise to that carry blood to plates of hepatocytes

Question 15

What is the Space of Disse?

Answer 15

A place where the hepatocytes are directly bathed by plasma (too small for cells)

Question 16

How is a hepatic acinus organised?

Answer 16

Zone 1: best O2 supply

Zone 2

Zone 3: worst O2 supply (closest to central vein)

Question 17

Which zone’s hepatocytes are the first to die if there are toxins or metabolites?

Answer 17

Toxin: Zone 1 dies

Metabolites: Zone 3 dies (low concentration of nutrients)

Question 18

What are the differences in the three zones in hepatic acini?

Answer 18

Zone 1: high in O2, toxins, nutrients

Zone 3: low in O2, toxins, nutrients

Question 19

How is bile produced?

Answer 19

Hepatocytes (bile salts from cholesterol)

Question 20

Which direction does bile flow in the liver?

Answer 20

Outwards (collected into ducts)-opposite direction to blood

Question 21

How is bile reabsorbed?

Answer 21

In the small intestine (concentrates bile salts and pigments), approx 90%

Question 22

How does the gall bladder know when to contract to secrete bile?

Answer 22

Fat–>CCK into blood–>gall bladder contracts–>relaxation of sphincter of Oddi–>squirt of bile into duodenum

Question 23

Where do the ducts draining the pancreas join the common bile duct?

Answer 23

At the sphincter of Oddi

Question 24

Why doesn’t the pancreas digest itself?

Answer 24

Zymogen enzymes are secreted in an inactive form and activate upon hitting bile/other enzymes